The truth is the whole. Of course, we cannot really see the whole, but it warns us to pose a problem as bigger than we would have, with further reaching ramifications.
— Richard Lewontin and Richard Levins, Biology Under the Influence
There’s not a great definition of wetlands. That seems right since they aren’t any one thing. Textbooks talk about the presence of water, about “unique” soil, about vegetation that’s adapted to moist conditions, but then add, “Wetlands are not easily defined.” 1 When is soil so damp that it becomes marsh? Or a river dry enough to be mud?
Neither land nor water, maybe both, a marsh is a balancing act, a collaboration between changing elements, uncertain by its very nature, in flux. As tides and temperatures rise and fall, wetlands adjust. Today, sea levels are creeping up, flooding those wetlands we call tidal marshes. If we want them to continue — if we want the communities of plants, birds, fish, and microbes that depend upon wetlands to continue (not to mention our own culpable species) — it’s important to figure out how a marsh works, how it survives, why. 2
Different species know the “why” of wetlands in different ways. For certain snails, the landscape consists largely of the green-yellow surface of marsh grass, where they graze for fungi. Various bacteria “know” a wetland by pulling energy from its mud. 3 We humans seek to understand through our own methods, including observation, speculation, experimentation. Faced with complexity, we often isolate a part of the whole and, from that, try to see the larger picture. So, scientists can be found drilling down into the muck of wetlands and pulling up dark, dripping cores. 4 These cylinders of peat offer a glimpse into history: what grew in the wetlands and surrounding watershed, how they’ve reacted to various climates, how people have affected the landscape. What the cores reveal is, in the end, a history of change.
Scientists can be found drilling down into the muck of wetlands and pulling up dark, dripping cores. These cylinders of peat offer a glimpse into history.
Like snails inching along a blade of grass, researchers pore over this history in various ways. Magnify a thimbleful of mud and you can count fossil pollen and spores. Burn a sample of peat, and you can measure the marsh’s past plant growth (or loss). Wash a bit over a fine screen, and you can pick through remains of seed, leaf, beetle leg, fish scale. The cores give scientists a basis in fact, a ground from which to speculate on how a marsh began, how it’s changed, and how it might continue to change. To ask “why a marsh?” is to try to picture the connected whole: the different grass and sedge and how they react to different tides, the various species of minnows that feed among the plants’ roots, the eye of a great blue heron tracking the minnows from the creek bank. Not only is the marsh a collaboration, but so is the inquiry into the why of it — a collaboration between numbers and sensation, between the quantitative and the qualitative, between (let’s say) science and poetry.
Before Europeans arrived, what is now the continental United States had more than 200 million acres of wetlands — an area twice as big as California — distributed along rivers, in prairies, by oceans. More than half that has been lost to agriculture, housing, environmental change. From the early 1950s to the early ’80s, during the postwar suburban build-out, the country lost over half its remaining marshland. 5 More recently, sea level rise has taken 20,000 acres of marsh along the Atlantic, 140,000 on the Gulf Coast. While the rate of loss has slowed to under three percent annually, the prediction is that almost half the tidal marshes that remain will disappear by the end of this century. 6
The prediction is that almost half the tidal marshes that remain will disappear by the end of this century.
Attempts have been made to put a value on this loss; the value varies, again, depending on the perspective. A marsh on the Atlantic coast of North America can provide habitat for minnows (mummichog, killifish), grass shrimp, Atlantic silverside. Its shallows offer feeding grounds and protection for American eel, striped bass, various crabs. The birds that nest or pass through include grebe, bittern, sparrow, hawk, heron. Dig down, and the muddy soil is home to communities of segmented worms, fly larvae, fingernail clams. 7 To a mummichog, a tidal salt marsh is essential for survival. To a predator — say, a red-tailed hawk — the value changes with the season and the prey: young birds in the spring, mice scrambling over winter’s snow. Trappers may value a marsh depending on how many muskrat live in the reeds, where developers see inexpensive land and the chance to make a different kind of killing.
‘Why a marsh?’ might be as vital a question to our species as it is to mummichogs.
In this era of global warming, a recently added measurement of value is carbon storage or “blue carbon”: the amount of carbon a tidal marsh retains as part of the (blue) ocean system. As our airplanes and cars and factories pump carbon dioxide into the air, a salt marsh captures some of that through photosynthesis and effectively “buries” it — and at a rate three to five times that of tropical forests. 8 According to one recent study, an English salt marsh is worth $800 an acre in the carbon it stores, “greater than any money that could be made from growing crops or grazing animals on it.” 9 Around the world, the estimate is that wetlands store some 17 million metric tons of carbon a year. That storage is starting to look crucial. The more carbon dioxide in the air, the more temperatures climb — which creates ice melt — which produces rising seas. As seas flood the marshes, the balancing act tips, the wetlands turn into river or ocean, and the carbon that has been stored in a marsh is released back into the air and water, feeding the heating cycle. “Why a marsh?” might be as vital a question to our species as it is to mummichogs.
The east coast of North America has been a prime area for tidal marshes, thanks in part to how deeply the region’s rock has been gouged out over time. During the last ice age, glaciers carved channels that allowed for an immense river system. The Hudson River flows through one of those channels, in this case forming a fjord where fresh water drains out to the ocean, distributing soil and seeds, while the ocean rushes in twice daily, bringing saltwater species, oxygen, and nutrients. In this mishmash of forces (what scientists call “a dynamic equilibrium”), both brackish and freshwater wetlands have sprung up. 10 How they’ve grown and how much carbon they’ve absorbed varies. A recent example: in 2011, tropical storms Irene and Lee dumped a massive amount of soil into the Hudson, much of which never flowed out to sea but instead remained along the river bottom or else got entangled in the mesh of roots and stalks that make a marsh. By increasing the sediment in the already murky Hudson, the storms may have added to wetlands, helping them lift (temporarily?) above rising tides.
Once, whole stretches of the Hudson were soft with wetlands, lining the coves and inlets, reaching out into open water. But starting two centuries ago, nearly all the shoreline between New York City and Troy was hardened with seawalls, railroad beds, breakwaters. 11 Many areas were dredged or filled, as if the uneasiness of a marsh — neither land nor water, therefore “unproductive” — had to be resolved one way or the other. Ironically, an estimated half the marshes currently on the Hudson have resulted from human interference: smaller wetlands tucked behind railroad tracks or growing on dredged fill. 12
Hugging the western shore of the Hudson about 25 miles north of New York City is Piermont Marsh. Extending out from Tallman State Park, it’s almost two miles long and reaches a third of a mile into the river. Not only its size but its sensitive location — between salt water and fresh water — make its history particularly telling. It’s a prime spot, in other words, to ask: “why a marsh?” Three decades ago, the federal government recognized the rarity of such a large stretch of tidal marsh, and Piermont became part of the National Estuarine Research Reserve. 13 Behind it are the abrupt cliffs of the Palisades; beyond them is suburbia: tree-lined streets with single-family homes, condominiums, ball fields, sewage treatment plants.
The present Hudson River is, among other things, more than 300 miles of runoff for mountain streams, creeks, tributaries. While it’s changed course over the eons, there’s been some wash of water and soil running through the area that is now Piermont Marsh for at least five million years. 14 From 2.5 million years ago to the relatively recent 17,000 years ago, ice covered the region at intervals: glaciers retreating and advancing, thick enough during some periods to cover the Appalachians. The ice pushed boulders and dirt before it, the last advance creating a huge dam of rubble at what is now called the Narrows, between Staten Island and Brooklyn. Once the dam was in place and the glaciers began to melt, a series of large, interconnected lakes formed. 15
Scientists pieced together the location of the lakes by using old surface maps and evidence from test borings and wells. Lake Hackensack occupied the flat lands west of what is now Piermont Marsh. It existed for a couple thousand years, covering what is now northern New Jersey and southern New York. 16 About 17,000 years ago, it found the first opening in the Palisades north of Manhattan: a fault in the bedrock which produced a 110-foot-deep “hanging valley” we now call Sparkill Gap. For almost a thousand years, glacier water rushed through the Gap into the channel of the Hudson, scouring the area that would become Piermont Marsh. 17 When the glacial ice and water finally drained enough (maybe 13,000 years ago), the land rebounded, rising and effectively blocking Sparkill Gap. Lake Hackensack pivoted and began to drain south. As the warming continued, other pent-up lakes broke free and their combined force eventually washed out the dam at the Narrows. Now the ice-cold, backed-up waters could run into the Atlantic, cutting a deep channel. When the river had dug down enough — and the ocean had risen high enough — the motion reversed: salt water backed north with the tides, producing the present mix of salt and fresh. 18
The history of the Hudson can be read by boring into its underlying muck and rock.
The same way the cores extracted from Piermont Marsh help tell its story, the history of the Hudson can be read by boring into its underlying muck and rock. Early in this century, when a new bridge was proposed just north of Piermont Marsh, engineers began taking below-ground test samples. Over a hundred borings found bottom at 300 to 400 feet, but on the western shore of the river — the Piermont side — the drills never reached bedrock. There, the glaciers had ground out a gulf estimated to be almost 750 feet deep. After the dam at the Narrows breached and the glacial lakes drained, the rushing back of the Atlantic was a little like the sea level rise we’re experiencing now. It pulled sediments into the channel and drowned marshes along the shore. And so, about 30 to 60 feet down into the mud, the borings found long-buried layers of sand and peat. 19
For plants to flourish in the Hudson’s mix of tide and current, they need protection. A point of land just north of Piermont Marsh sheltered its first seedlings. To the south, the curve of the shore buffered the marsh, allowing it to expand into a long low plain. At first the marsh was more water than land; the remains of one-celled marine creatures confirm that it flooded frequently. Over thousands of years, the marsh rose, trapping sediment, building on the debris from plants, keeping up with the advancing water. Finally, when sea level moderated to where it was only rising about four inches per century, the soggy meadow along the Palisades established itself as high marsh. It had, in effect, insulated itself from the greater environment, setting up a particular world where factors like salt and tide determine what can survive. 20
By the time this section of river had turned into Piermont Marsh, humans had been in the valley at least 5,000 years. They seem to have been wanderers, migrating through to hunt and gather. Mastodons and other herbivores lived in the valley, too, foraging on marsh grass; there’s some evidence they were hunted to extinction. 21 Native American wise men — sachem —passed on stories of ancestors confronting giant creatures and surviving in a landscape of ice and snow. Boulders were scratched with images of strange animals, and now and then, the river uncovered an ancient spearhead from an era almost pre-memory, when ice shrunk the seas and the shore extended out for miles. Other artifacts — knives, butchering tools, weights for fishing nets, shucked oyster shells — date back some 3,000 years. The variety of arrowheads suggests that numerous tribes were using the river, returning to spots where the shad ran or the beaver were plentiful or it was easy to get to the oyster beds. Soon, there’s evidence of semi-permanent settlements, often at the mouths of tributaries like Sparkill Creek. (Workers on a railroad line being put through Piermont in the 1840s found a cache of shucked oyster shells that sediment had buried five feet underground.)
On April 17, 1524, the Italian Giovanni da Verrazzano sailed in off the Atlantic and anchored at the mouth of the big river. The Hudson valley was almost entirely forested. The rocky, wooded island called Mannahatta was ringed with wetlands. 22 Along both shores were Lenape people speaking Munsee dialects of Algonquin, a language group that extended into the Great Lakes and farther west. The tribes lived in small settlements: the Wecquaesgeeks on the island’s rocky north, across the harbor the Hackensack and the Navesink. Near what would become Piermont Marsh, in the shadow of the bluffs that natives called Wee-Awk-En — “rocks that look like trees” — were the Tappan.
For thousands of years, humans took what they needed from the marsh but, according to the plant records, left it mostly unchanged.
Like other tribes in the region, the Tappan survived thanks to the Muhheakantuck, the “river that flows both ways.” They seem to have had fishing villages at both ends of Piermont Marsh. They built weirs of branches and reeds to catch sturgeon — wisahosid — and wove long nets of tree bark to trap shad on their spring migration. They hunted kwikwinkëm — duck — probably ate marsh birds, the eggs and young, and gathered edibles like glasswort and cattail roots. 23 Occasionally they would kill the whales and seals that swam up the estuary. At night, the Tappan hunkered by slow-burning fires, wearing raccoon grease to try and keep off the mosquitos. 24 Lenape women shaped the clay from glacial lakes into pots and planted gardens of beans and squash in the rich soil deposited by spring floods. In the winter, the Tappan probably went inland to escape the cold, with trips back to the marsh to trap beaver, muskrat, otter. They mixed salt hay from the marsh with clay to insulate the chinks in their longhouses. For thousands of years, humans took what they needed from the marsh but, according to the plant records, left it mostly unchanged.
How do we attempt to read the “pre-history” of Piermont Marsh and its nearby forests? In a relatively undisturbed section of wetlands, a team of researchers drives an auger-like tool called a Dachnowski peat corer down through the first foot of dense roots, then through another foot or two of muck, until they hit “a more solid substrate” of peaty remains. 25 They then extract a three-foot core. To sample below that, they work a modified Livingston piston corer — a two-inch hollow steel tube — down into the peat, stopping every three feet to pull, label, and wrap a mucky “sausage” sample. They then push the tool back down, adding extensions as they go. By the time the peat is too compacted to go any deeper, the scientists have extracted about a 45-foot core.
It seems a primitive science: bent over a bit of mud, picking out seeds and pollen, comparing them to a collection kept in an antique cabinet.
Back in the lab, the researchers first focus on the top sixteen feet. The mass spectrometer at Lawrence Livermore National Lab in California dated an identified macrofossil from this part of the core back to over 2,000 years ago. The next step is to put thimble-sized samples of peat into test tubes, then spend two days boiling these in various acid mixtures, centrifuging and rinsing to destroy all minerals and peat. That leaves the pollen and spores, which are dehydrated in alcohol and suspended in silicone oil. Finally, the researchers magnify times 400 and starts counting, identifying at least 300 pollen and spores per sample.
It seems a primitive science: bent over a bit of mud, picking out seeds and pollen, comparing them to a collection kept in an antique wooden cabinet at Columbia’s Lamont-Doherty Earth Observatory. But the painstaking identification helps fill in a picture of a changing watershed and lets the researchers ask larger questions. What were the various eras in the marsh’s history? How did its living communities balance and re-balance their shifting collaborations? Does that history help predict the future?
According to the cores from Piermont Marsh, between 653 and 1292 the local woods were dominated by oak and pine, with a scattering of other species, including chestnut. These were high canopy forests in whose shadows the Tappan and their ancestors hunted deer, fox, bear, pheasant. The cores show there was probably more pine than we find today, making a soft bed to walk on. Over these six centuries, an increase in hickory and decline in beech indicates a warming trend. That’s matched by more mineral sediment (that is, more silt in the peat), a sign of upland erosion. In this, the oldest of the examined cores, there’s a lot of stored carbon: near the maximum for comparable marshes, even those of the warmer southern wetlands that might be expected to be more productive.
Other studies have established that, between 795 and 1290, there was a heating up of the earth in North America, Greenland, Europe: the Medieval Warm Period. Temperatures rose only a few degrees, but that was enough to mark the era. 26 From tree rings in North Carolina to lake records in central Massachusetts, there are signs of greater heat and drought. In the Hudson valley, rainfall (and so streamflow) decreased by as much as half; that meant less fresh water running downstream, and more salt water flowing upstream: the ocean creeping in. 27 The Piermont cores from this period — dark gray mucky peat — turn up more alder and willow pollen, from trees with fibrous, water-seeking roots that colonize riverbanks when the water level drops.
During the Medieval Warm Period, temperatures rose only a few degrees, but that was enough to mark the era.
There are also lots of charcoal fragments. 28 Some may have come from a distance, carried downstream by the Hudson, but their size signals that many fires were local. In some of their first written records, the European colonists observed that the natives “burnt up all the underwoods in the Countrey, once or twice a year … [producing] great Parkes, and … great Forests.” 29 The Lenape were said to use fire to force out prey, to open the forests for easier hunting, to clear brush to plant gardens. It’s even possible they set fire directly to Piermont marsh, as colonists later would, to reduce mosquitoes and chase out game. 30 But the amount of charcoal and evidence of marine elements argues that drought, not people, was the main cause of fire. The drier, pine-dominated forests of the warm period were that much more susceptible to lightning and the like. This helps explain the increased erosion, as the burnt hills (without the binding of living roots) gave up their topsoil. Sparkill Creek and the Hudson would have run darker, dirt clouding the already clouded waters. 31
There’s very low carbon storage during the Medieval Warm Period. The shift from oak towards pine, hickory, and willow meant a denser, less open forest. When this landscape, dry as tinder, caught, the flames sent stored carbon up into the atmosphere instead of decaying on the ground and finding its way into marsh peat. Finally, the dryness probably led to wetlands loss. Infrequent rain meant smaller standing ponds in the high marsh, reducing the habitat for killifish and shrimp, producing that much less food for herons and other predators. 32 That scientists found less pollen in the samples from this period probably signals fewer plants overall; the green buffer between land and water was shrinking.
Still, from before the Lenape arrived until as recently as one hundred years ago, the overview of what we now know as Piermont Marsh remained basically the same: a low, green, matted wetlands stretching out from the shoreline, water often visible at its roots, the ground giving way under foot but never quite collapsing. This was the high or Spartina marsh, dominated by cordgrass, Spartina patens, and by salt grass, Distichlis spicata.
A salt marsh never quite reaches equilibrium between the water flowing in and the soil building up.
A salt marsh never quite reaches equilibrium between the water flowing in and the soil building up. It may look like equilibrium, given enough time and distance, but the factors keep changing. Piermont Marsh gets flooded ten to twelve times every month; between an inch and eight inches of water cover the marsh for three or four hours; storm surges can bring even more. Drainage happens back over creek banks, down into the peat, and up into the atmosphere through evaporation. On the interior, the water table is only about four inches down. Closer to the creek, the water drains faster and rises faster. How much faster helps determine the wetness of the marsh, of vital interest to the species that live, hunt, and nest there. But even during low tides — and hot summers — the marsh stays wet. 33
Spartina and Distichlis thrive in this environment. These grasses help answer the question: “Why a marsh?” Or, more specifically: “What can live between land and water?” They end up the dominant species by adjusting to, or collaborating with, salty water. Because Spartina alterniflora can survive twice-daily immersions, it’s one of the first plants to establish itself in tidal areas: the colonizer. Spartina’s flooded roots draw the brackish water up into its cells; the cells concentrate the salt; glands on the surface of the grass then extract the excess salt and expel it. The matted, swirling cord grass of a high marsh often glistens with tiny salt crystals, until they’re washed off with the tide. And the roots of Spartina patens have a “communal effect” on the mucky soil, penetrating it and bringing in more oxygen, making it easier for the grass to spread. 34 The interwoven root system and its associated fungi fight erosion, harvesting nitrogen from the air, creating a dense meadow environment. That environment allows certain other plants to grow, feeds various insects from passing butterflies to hunting spiders, and harbors marine species.
At high tide on a hot summer day, the briny water that floods the grass is alive with tiny creatures between four-one-hundredths and eight one-hundredths of an inch. Under a microscope, they turn out to be teardrop-shaped, with antennae and a tail but no stomach or throat. These are the young of the most abundant animal in the estuary: copepods, tiny crustaceans, hard-shelled creatures that are almost transparent. These copepods swirl through the water, feeding on single-celled organisms and bacteria. They get hunted, in turn, by striped bass larvae and killifish, which swarm into the warm marsh, looking for prey. Scientists suggest that this miniature drama is one way carbon passes through the system: from plants to bacteria to copepods to fish and onward. 35
The cores from Piermont Marsh offer up evidence of a radical climate change beginning between 1292 and 1418. More hemlock and beech joined the pine and oak forests, a sign that the uplands had passed out of the drought and grown wetter. Pollen from narrow-leafed seaside plantain, a plant of the high marsh, shows up for the first time. So does flowering dock, fringing the yellow-green marsh with a tall “weed” that turns rusty brown in the fall. This long century is a transition from the warming trend, our cores going from dark gray to a blacker muck, as climate records indicate “complex sea-level variations.” 36 That researchers start to see more cattail pollen indicates there’s more fresh water in and around the marsh. On top of these signs of climate change, more evidence of ragweed turns up in the cores, perhaps a sign of Indigenous people altering the landscape.
Before the arrival of Europeans, the marsh peat shows a high level of nitrogen, which can be read as an indicator of wildness. The great flocks of ducks and birds that lived and bred in these wetter wetlands — their grazing and guano — may have changed the chemical makeup of the marsh. 37 At the same time, the amount of charcoal in the samples drops; in a wetter forest, there were fewer fires and, so, less erosion. The region was transitioning into cooler, moister conditions that would lead, around 1400, to the Little Ice Age.
During the Little Ice Age, temperatures dropped by only a degree or so, but glaciers grew, the Baltic Sea froze, pack ice blocked the Atlantic.
During the Little Ice Age, temperatures dropped by only a degree or so, but mountain glaciers grew, the Baltic Sea froze, pack ice blocked the Atlantic. For humans and other species, hunger and starvation increased; populations declined. The black muck cores from the early 15th to late 17th century show more oak, birch, spruce, hemlock, and beech: northern trees. In the Ice Age, summers were shorter, the growing season brief; and so less carbon was stored in Piermont Marsh. Ice on the river, floating slowly down from the north (sometimes carrying a bald eagle that surveyed the chill waters) had the weight and leverage to carve off sections of the marsh, carrying the peat — and with it the “blue carbon” — downstream to the Atlantic. 38
As Europeans started moving into the area of Piermont Marsh, they observed the Tappan and others struggling to survive the cold. As late as the 1830s, the diaries of Piermonter Nicholas Gesner recorded frosts in late summer, compared to mid-October in this century. 39 The cores again carry more ragweed — a sign of soil disturbance — as brush and forest may have been cleared for larger gardens, more hunting grounds opened in a wider search for game.
Henry Hudson came upriver in 1609, passing the large marshes on both banks, mooring near Piermont before continuing north to present-day Albany. Dutch settlers followed almost immediately, their primary economy the fur trade. The large population of beaver — nearly every body of water had some — was eliminated in short order. Fewer beaver dams meant less still water in the tributaries and disappearing wetlands. 40 At the same time, Dutch farmers erected their own dams to provide power for grist mills, and the mill ponds held back sediment that would otherwise have found its way to the Hudson and its marshes. By the 1630s, Europeans had taken over large tracts of land that they managed by importing and enslaving Africans to work the land. The Dutch acknowledged the Indigenous people by calling the “sea” near Piermont Marsh the Tappan Zee, but they crushed a mid-17th-century Lenape rebellion, and natives were soon forced out or killed. 41
The coming of Europeans is reflected in the grayish-brown cores, which show more ragweed and goosefoot and less pine, oak, chestnut: the forests are being cleared.
The coming of Europeans is reflected in the now grayish-brown cores, which show a good deal more ragweed and goosefoot and less pine, oak, chestnut: the forests are being cleared to make way for farms and roads, to provide wood for ships and houses, for fuel in winter. In the late 17th century, there were just a couple hundred people in the county that includes Piermont Marsh; a century later, there were several thousand. During the Revolutionary War, nearby iron mines increased production with more trees cut to produce more heat for more forges turning out more weapons. Sawmills supplied lumber wherever there were trees and waterpower — then were moved when either supply ran out. 42 The hills and mountains were all but denuded, reflected in the cores by less organic sediment (less forest) and more inorganic (sand, silt, clay).
One reason the cores from the time of European settlement show less blue carbon is that salt grass wasn’t left to die its “natural,” carbon-storing death. Look at the paintings of Martin Johnson Heade, made in the mid to late 19th century. Heade liked to paint large canvasses of salt marshes, taking advantage of the long, flat horizons and the play of light in an uncluttered landscape infused with salt air. But he also included signs of human activities. In his painting Newburyport Meadows (ca. 1876–81), we see a tiny man driving a tiny wagon pulled by tiny horses; he’s haying, cutting and going out on the marshes in the fall to cut and stack the cordgrass, which provided livestock not only feed but a built-in quantity of salt. Heade shows great, beehive-shaped haystacks towering over the farmer: piles of stored carbon to be hauled inland to cattle barns.
An 1887 survey of Piermont Marsh records 174 separate land allotments for harvesting. 43 To get their carts and horses out on the shuddering surface of the marsh, locals dug ditches, cutting channels for water to drain, making the wetlands that much less wet. (This was also thought to control mosquitoes and greenflies by draining breeding sites.) Ditching meant a shorter time for tides — and nutrients — to feed plant life and fewer breeding areas for fish and birds. 44 In her 1885 novel, A Marsh Island, Sarah Orne Jewett describes a scythed autumn marsh as “soft and brown now, and even a cold gray where the grasses had not grown since the salt hay was gathered.” 45 Less salt-tolerant plants, like cattail, could now take hold. A snapshot from the 19th century shows Piermont Marsh on a snow-covered day: the marsh is ditched, some of it squared into fields, with dark mounds of mowed hay waiting to be taken in.
After the Revolution, the population of New York City increased from about 23,000 in 1786, to about 123,000 in 1820; farming spread to feed the growing city, with more salt hay needed to feed more livestock. The creek that ran out into Piermont Marsh became a port of entry, allowing locals to get their produce to the river and receive goods in return. Inland, the trading town of Tappan prospered, and the creek became known first as Tappan Slote, then Sparkill Creek. A later photograph shows small wooden sloops pulled up onto the marsh grass, their spars sticking up above the “kill” (Dutch for creek).
The Piermont cores reveal the beginning of the marsh’s industrial era to be around 1822, when there’s a jump in lead, copper, and arsenic.
The Piermont cores reveal the beginning of the marsh’s industrial era to be around 1822, when there’s a jump in lead, copper, and arsenic. In 1828, the small town that was growing up around Sparkill Creek raised funds for ferry service to New York City, and the steam-powered Orange began traveling daily from a pier just north of the marsh. Forests were cut to provide fuel for the ferry; streets were stacked with “huge piles of cordwood.” 46 Ferries and steamboats demanded deeper channels; the resulting dredging both eliminated marshes and, by dumping fill, created opportunities for new ones. 47 Soon, the steamboats that had displaced sloops were themselves threatened by railroads. Developers expanded the point of land north of the marsh, bringing in countless wagonloads of fill to create a 4,000-foot-long pier “on what had been marsh and open water.” 48 By 1851, freight and passengers could sail up the Hudson on a steamboat from Manhattan, dock at the new pier, and board a train to continue the journey west to Lake Erie.
The railroad pier made and named the town, which was incorporated as Piermont in 1847. Hotels and markets appeared near a roundhouse that could handle 30 locomotives. A local judge built a road across the marsh to develop a neighborhood of cottages on high ground; a police officer was hired; streets were improved; the population grew to 1,200. 49 An 1852 oil painting by Jasper Francis Cropsey shows a steamboat docked at the pier, cows grazing in the foreground, the town in the distance, a train chugging inland through the marsh. 50 The core samples reveal more birch, a sign of disturbed and lumbered forests, as tanneries had hemlock felled to the point of forest exhaustion and nearby brick factories clear-cut oak and pine for fuel. Within twenty years, though, the railroad lines were running directly to New York City, and Piermont’s life as a transportation hub ended. Once again it became a placid river town with an economy based on selling produce to the city. In the summer of 1860, the region supplied New York with 180,000 baskets of strawberries, along with fresh milk and cream. 51
The post-Civil War boom had little effect on Piermont’s population, but industrialization was changing the region’s balance. A few years after the war, the Hudson River was declared “contaminated” 52; by the end of the century, shad and sturgeon had been overharvested, and Piermont’s last commercial oyster business closed. 53 In 1901, a paper mill near the former railroad terminal began using water from Sparkill Creek to power its turbines and flush its waste. The mill grew to be the economic center of the town, employing some 1,300 people. “Steaming vats of pulp and hot glue,” the fumes and gases from production, all contributed to polluting the water and, by extension, the marsh. 54
A news article from the 1930s complained about “the unsanitary and unhealthy conditions of the salt meadow,” and reported a proposed 200-foot dredging project to deepen Sparkill Creek and “eradicate the existing evil.” The idea was to straighten and thereby flush the creek, getting rid of a “nauseating conglomeration of decayed matter.” 55 That might have been the end of the marsh — dredging traps sediment in the deepened channel, slowing the rate of wetlands growth, leading to what’s known as “marsh drowning” — but the dredging never happened. The creek continued meandering to the river, carrying sediments, pollen, and pollutants up into the grasses.
After World War II, as the suburbs expanded, the forests that had been Lenape hunting grounds re-emerged as tree-lined streets.
After World War II, as the suburbs expanded, the forests that had been Lenape hunting grounds re-emerged as tree-lined streets. In 1955, the Tappan Zee Bridge was completed a couple miles north of the marsh and the local population increased exponentially. The lower Hudson was now receiving untreated sewage from some six million people. 56 A section of Piermont Marsh near the paper factory became a municipal landfill, with cottonwoods rooting among the junked cars. As housing swallowed up more open land, the marsh cores show signs of the increased nitrogen fertilization that came with suburban lawns and sewage treatment facilities. More people living near the marsh was altering its very composition. 57
In the middle of the 20th century, the view from Sparkill Creek changed fundamentally from what it had been since before the Lenape arrived. A tall, fuzzy-topped reed called Phragmites started forcing out the cordgrass, salt grass, and sedges, altering the balance of land and water, creating a new dominant community. The Piermont cores show the first signs of Phragmites around 1200, but it doesn’t become firmly established until 1900. The reed that begins to take over Piermont Marsh is not the native kind but a hybrid type more common in Europe and Asia. It apparently arrived in the late 1700s in ship ballast from Europe and, in what’s been described as a “cryptic invasion,” took over, eventually turning Piermont’s low-lying green marsh into a golden field rising eight to twelve feet. 58
Paddle through on one of the marsh creeks, and the Phragmites to each side forms a seemingly impassable crisscross of stalks with an occasional tangle of bindweed or aster. Step in, and you’re surrounded. What you walk on, bending and breaking the reeds as you step, is black muck covered with stalk fragments, water oozing up under your feet. With each step you sink down a couple inches; if you jump, the “ground” shakes in response. You startle no birds, scare no fish, because there don’t seem to be any. Through the gold bars, you can make out a distant pond and hear a Canada goose; otherwise, it’s all reeds — still in the bright sun or scratching slightly with a breeze.
A Phragmites marsh offers its own food web, but its monolithic presence in Piermont appears to have eliminated plants, birds, fish, and insects.
In the mid-1960s, Phragmites made up about 40 percent of Piermont’s plant life; by the early ’90s, more than 65 percent, the reeds advancing around 13 acres a year. In the first decade of this century, the interior of the marsh still grew patches of salt hay, spike-grass, bulrush, and cattails — a variety of plants that welcomed a variety of inhabitants. But Phragmites soon accounted for more than 90 percent of the marsh’s plant life. By 2017, the New York State Department of Environmental Conservation found Piermont’s high Spartina patens marsh “notably absent,” the last remnants hidden near the center of the changing wetlands. 59 A Phragmites marsh offers its own food web, but its monolithic presence in Piermont appears to have eliminated plants, birds, fish, and insects. And because Phragmites is so dense and sheds that much more litter — dead shoots, stems, leaves — it changes the community, smothering other plants, extending its own success. 60 The litter also holds back the tidal flow, especially to the interior of the marsh, which shrinks the wet surface area occupied by minnows. To a spotfin killifish, which prefers a high marsh dominated by Spartina patens, the “value” of Piermont Marsh had changed radically. 61
Historic records show the marsh was habitat for pied-billed grebe, clapper rail, and night heron, among others. While there are still nests of marsh wrens, probably least bittern, and certainly Canada goose, the taller, denser environment of the reeds may have driven out other birds. A study of an upriver marsh connected the invasion of Phragmites to a decline in least bitterns, Virginia rails, marsh wrens, and swamp sparrows. 62 Back in 1889, an ornithologist reported both saltmarsh sparrow and seaside sparrow “abundant and evidently breeding” in Piermont Marsh. But with the loss of Spartina to reeds, the population of saltmarsh sparrows has declined nationally by 75 percent since the 1990s. 63
On a breezy fall day, the dark creeks of Piermont Marsh are dotted with fluff — airborne Phragmites seeds. They’ve helped spread the invasion across the length of the Hudson estuary, seeding disturbed areas, drainage ditches, construction sites. In Piermont, the reeds seem to have spread from the edges to the center, their roots invading open patches of mud, changing the composition of the soil. 64 Examine the damp mud under the reeds, and it’s knobbed with stems, sharp to the touch, hard underfoot. At the outermost edge of the marsh, facing the river, you can still find some outcroppings of Spartina alterniflora, but the former colonizers are now remnants; behind them is a wall of reeds ready to take over whatever new wetland gets established.
A Village of Piermont report noted that, between the 1960s and 1990s, a lot of the drainage area that fed Sparkill Creek was “paved over and built upon.” 65. That’s meant less brush to absorb runoff and more frequent and higher flooding. This ended up helping the reeds, which prefer fresher water and seem to be more tolerant of certain kinds of pollution. 66 But what probably spurred the reed’s invasion was an increase in nutrients. When a limited amount of nitrogen fed the marsh, Spartina’s root system won out, producing its mats of grass. But when modern times brought a nitrogen “surplus” (some of it from fertilizer runoff), both plants were enriched below ground, and the competition shifted to which could get the most sunlight. Here, the reeds’ height advantage left the grasses in shadow. What we see in Piermont Marsh is happening from Massachusetts to the Gulf of Mexico: more nitrogen and phosphorous has produced more growth above ground, less below, for a gain in height but a net loss in marsh soil strength. 67
Today, the eight-mile creek is webbed by almost 300 miles of sewer lines.
The Piermont cores confirm this spike in nitrogen; and there’s another likely source beyond runoff. In 1959, a few years after the new bridge boosted development, a town sewage treatment plant opened near Sparkill Creek, followed less than a decade later by a larger county facility. Today, the eight-mile creek is webbed by almost 300 miles of sewer lines. Every year the plants treat 14 to 17 billion gallons of waste; every day they discharge 30 million gallons into the river just off Piermont pier. 68 By the 1990s, the Village of Piermont was describing how the lines “periodically stink and overflow.” 69 Water studies of Sparkill Creek repeatedly find its raw sewage infiltration “chronic and severe,” with peaks that a microbiologist at Columbia’s Lamont-Doherty calls “extremely high.” In 2013, a resident on the creek was reporting “repeated catastrophic blowouts of the sewage system lines … [causing] enormous surges of sewage to run into the creek and, of course, the Hudson River.” New York State has listed Sparkill Creek as one of its most polluted, nitrogen-heavy tributaries. 70
The present-day Piermont Marsh is what urban ecologists call a ‘remnant native landscape.’
The present-day Piermont Marsh is what urban ecologists call a “remnant native landscape.” Its reed beds are a product of human interaction, from seeds arriving in ship’s ballast to the nitrogen bursts from sewage blowouts. Or, as the state’s Departmental of Environmental Conservation puts it, “The abundance of Phragmites makes it impossible to classify the majority of the marsh as a natural estuarine community.” 71 This shift from salt meadow to reed bed appears to have happened with little to no public discussion or protest. In the mostly residential neighborhoods that grew up around the marsh in the mid-20th century, wetlands weren’t “useful,” and were often synonymous with wasteland. They bred biting insects; they smelled “bad”; their soil was too wet to build on or plant. Since then, there’s been a change in the balance of human opinion about the balance that is a tidal marsh (see the 1972 Clean Water Act, improved sewage treatment starting in the 1980s, etc.). But enforcement of environmental laws varies under different administrations, and manmade stress factors continue to cause “marsh dieback.”
In Piermont, the shift to Phragmites threatens, as one report puts it, “the diversity of life and services that make the marsh an extraordinary and special place.” 72 Scientists have found that reed marshes still support mummichogs, grass shrimp, little river herring — but there are fewer than in the former Spartina marsh. That suggests the drama of striper larvae hunting tiny crustaceans is happening less often and with less success. Meanwhile, below ground, a Phragmites marsh attracts only half as much of the fungi that help “sink” carbon.
Which brings us to the future.
Temperatures on the planet are predicted to rise about two-and-a-half degrees in the next few decades, higher by the end of the century. That’s greater than in the Medieval Warm Period, and will lead, if history is any guide, to droughts and a buildup of nutrients that can choke off plant and animal life. As with earlier glacier melts, the melting of ice sheets in Greenland and Antarctica is already raising sea levels, creating a decline in southern New England Spartina marshes. The future climate is likely to be one of extremes. A recent report on Piermont Marsh found a trend towards warmer water and more salinity — a change that’s likely to accelerate as, among other things, the “blue carbon” formerly buried in marshland escapes into the atmosphere. 73
Plants, birds, fish, insects, one-celled creatures, and humans have grown up in and around the marsh and need it to breathe, to eat, as protection from the elements. This extended community —collaborative and interdependent — relies on a certain land/water balance. The main question may be simply how to make sure the marsh continues. But this is soon muddied by asking what it should continue as. The cores help show how Piermont Marsh has morphed over time, adapting to heat, cold, drought, and flooding. It’s going through the latest version of that, except the human factor in the current warming trend has that much greater influence — both on upsetting the balance and, potentially, restoring it.
Draining, ditching, burning, filling are all ways to alter wetlands to accomplish human goals — whether it’s more salt hay or fewer mosquitos, better hunting grounds or more housing.
Draining, ditching, burning, filling have all been ways to alter wetlands to accomplish human goals — whether it’s more salt hay or fewer mosquitos, better hunting grounds or more housing. Today’s reed-covered Piermont Marsh is a by-product of this 7,000-year human interaction. It’s maybe not the future anyone envisioned, but it’s a future we helped make. In response to recent changes, various proposals have been made to re-balance the marsh. New York State’s 21st-century vision of Piermont’s future included a proposal to severely reduce the amount of Phragmites and return the wetlands to something like the green Spartina-dominated marsh it used to be. 74 At one time, the plan involved mowing down about 200 acres of the reeds, then applying herbicide. Angry local residents worried both about the side effects of the herbicides and how “lowering” the marsh might make it less effective as a storm buffer. The state eventually made adjustments, eliminating the use of herbicides and reducing the test area to a quarter-acre.
A 2020 study found that Piermont Marsh was increasing its height by 0.2 inches a year; more litter from the monoculture of Phragmites may be helping that. But the Hudson rose about a foot in the 20th century and may climb as much as six feet by 2100. Should that happen, an estimated 90 percent of the marsh would flood. Faced with rising oceans, some tidal marshes can push inland, colonizing the shoreline; a recent study called this “the single most important way [to] offset or prevent” drowning wetlands. 75 But with its back against the slope of the Palisades, Piermont Marsh has nowhere to go, unless current residential lots are abandoned.
Rather than moving outward, the marsh may well be losing ground. Historical photos from the 1950s and ’60s show a Spartina marsh unbroken by ponds; today, its interior includes standing pools of water, and they seem to be expanding. The resulting waterlogged marsh may be shrinking from the inside out; at the same time, it may be eroding from the edges. The manager of the Hudson River Reserve, comparing today’s profile to old topography maps, estimates the marsh has lost some 50 feet of shoreline in the past hundred years. Authorities are considering building barriers of concrete or plant material: walls to keep change out.
The manager of the Hudson River Reserve estimates the marsh has lost some 50 feet of shoreline in the past hundred years.
For the marsh to survive sea rise, it needs not only to grow but something to grow on. With hardened shores and dams blocking the flow of sand, silt, and clay, industrialization can mean less sediment. In Jamaica Bay, New York, the U.S. Army Corps of Engineers has a $19-million project to use fill dredged from New York Harbor to create a “marsh island,” which is then planted with native species. Dredging in the Hudson could provide a similar source. Another way to add land is to modify or tear down some of the 1,700 manmade dams in the Lower Hudson Valley, including those on Sparkill Creek. That would release the mill ponds and the muddy soil that’s accumulated there over the centuries. By improving and expanding sewage treatment plants and fixing individual sewage connections, we could reduce the nitrogen that is speeding up peat decomposition, undermining marshes, and reducing carbon storage. Finally, we could encourage new wetlands. Some have sprung up where sections of the river have been filled or where construction has created little coves, and these marshes are trapping sediment faster than “natural” marshes, outpacing sea-level rise. But the new marshes are more reed and cattail than meadow, which means a reduced habitat for certain species and, possibly, less carbon storage.
All these interventions have a basic assumption behind them: that our species can answer “Why a marsh?” Or answer it enough to define a wetland, put a value on how it works, and therefore fix it. That’s “fix” in two senses: solve its problems, and somehow fix it in place at its optimal (to us) status. But as landscape architect Rob Holmes has argued in this journal, “The idea of fixing a landscape by making it permanently stable may be wholly incompatible with a healthy planet.” 76 That seems particularly true when it comes to wetlands, which remain in flux, responding to changing tides and plant life, temperatures and micro-organisms. Scientists continue to debate how altering one component of a marsh (building a retaining wall, for example) might affect others. We can, in other words, make real progress on analyzing, measuring, and “correcting” parts — and still find it hard to see the whole.
Studying soil cores gives us a chance to picture how Piermont Marsh has reacted to and stimulated change over thousands of years. It can help us see how intricate are the collaborations that produce wetlands, from the tiny salt glands in Spartina to the osprey diving for menhaden to the red oak dropping leaves in a distant forest. There are lessons here in observation, in systemic thinking, maybe even in humility.
Piermont Marsh will adjust to climate change, just as it responded to the Medieval Warm Period and to the Little Ice Age. But it may be difficult. A recent study found the wetlands on the Hudson, including Piermont’s, “some of the least resilient in the nation,” almost twice as vulnerable to rising seas as the national average and, because of hardened shorelines and other human interventions, much less able to adapt. 77
Piermont Marsh may die. The changeable balance that was wetlands will become river, and waves will lap at the base of the Palisades.
That leaves a final option: Piermont Marsh may die — either in part or as a whole. The most likely scenario is drowning: the banks of the creeks will slowly flood, first overtaking the lowlands where the Tappan took clay to make pots, then the high marsh that was once mowed by farmers. The rising tides will outpace the accumulation of sediment; the roots of plants will be soaked more and more often until they rot; the fibers that hold the muddy earth in place will dissolve; and the accumulation of peat — of history — will gradually wash away. The changeable balance that was wetlands will become river, and waves will lap at the base of the Palisades.
And then, over time, that may change, too. Whether or not there are humans to observe it, small green plants may once again take hold in a stretch of mudflats, neither land nor water.